Pac Man is my best friend.

Okay, not really. But as a child of the 80’s, video arcade games were a huge cultural phenomenon of my formative years.

Tiny affordable microcontrollers are a cultural phenomenon of today’s generation.

This project bridges the generations to create an animated LED necklace or charm that you can customize to create a retro-style personal “totem video game creature.” It’s a small project, good for electronics novices and group workshops. And you’ll have something eye-catching to wear and show off afterward.

This guide was written for the Trinket Mini and Gemma v2 boards. It uses ATtiny-specific features and DOES NOT WORK with the newer “M0” boards, nor on larger “AVR” boards like Feather 328 or Arduino Uno.

Tools Needed

This is a soldering project, albeit a small one. You will need the common soldering paraphernalia of a soldering iron, solder, wire (20 to 26 gauge, either stranded or solid) and tools for cutting and stripping wire.

Parts needed

  • Adafruit Trinket Mini or Gemma v2 microcontroller board (if Trinket, either the 3.3V or 5V type works). The newer “M0” boards are not supported.
  • Mini 8x8 LED Matrix w/Backpack (any color — we have several! Green for Space Invaders, yellow for Pac Man, etc.)
  • 3.7V 150mAh Lithium-Ion Polymer Battery
  • LiPo battery charger
  • JST Battery Extension Cable (Trinket only — not required if using Gemma)
  • Lanyard to create a necklace. This should be non-conductive — plastic lace (the sort used for weaving bracelets), rubber necklace cord or heavy fishing line all work. A pin back (such as our magnetic variety) is another possibility.
  • Optional: momentary pushbutton to activate the animation. You could substitute a vibration sensor switch to make it shake-activated. Or just use the tiny reset button that’s built into the Trinket or Gemma to restart the animation code.
  • Optional: If using Trinket, a bit of heat-shrink tube is best for covering some connections; it’s cleaner than alternatives like tape.
Can I use a “small” (1.2 inch) LED matrix instead of the “mini” (0.8 inch) version?
Sure can! Just be super extra careful to follow the assembly directions in the LED Backpack Guide and install the matrix the right way on the board. This is a common mistake! The “mini” matrix is recommended for this project because it’s less troublesome for beginners.
Can I use other color matrices?
Yes! You can use any color of our 8x8 matrices: red, green, blue, white...
Can I use the bi-color matrix backpack?

Potentially yes, but you will have to adjust the bitmaps and code to handle the extra rows (it appears like a 16x8 matrix to the driver chip). We don’t have a code or tutorial for this variation, but the wiring is the same if you’re inclined to try.

This guide was first published on Oct 01, 2013. It was last updated on Oct 01, 2013.

This page (Overview) was last updated on Nov 28, 2021.

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